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Introduction

Adult American Dipper, King Co., WA, 4 April.

Figure 1. Distribution of the American Dipper.

[H]is music is that of the streams refined and spiritualized. The deep booming notes of the falls are in it, the trills of the rapids, the gurgling of margin eddies, the low whispering of level reaches, and the sweet tinkle of separate drops oozing from the ends of mosses and falling into tranquil ponds.

John Muir’s “ouzel” or “water thrush” now bears the name American Dipper, a descriptive name that matches the names of this species’ European, Asian, and South American counterparts. The name describes the most conspicuous habit of most members of this family of aquatic passerines: a repetitive up-and-down bobbing motion.

Admirers of Muir’s ouzel have attributed to it a combination of factual and mythical characters. Muir declared “bird and stream...inseparable,” which is essentially true; although this dipper, like others, rarely strays from rushing streams, it does on occasion frequent lakes and seashores. It does not restrict itself to mountains; some individuals nest along coastal streams from Alaska to California and on desert streams in Grand Canyon and Zion national parks.

The American Dipper chooses a nest site, invariably along a stream, that usually provides security from floods and predators. The upper limit to population size appears to be determined by the availability of suitable streams and nest sites, and by territorial behavior where potential nest sites are close together. appears to limit its populations and is probably the principal limiting factor. It eats an exclusively animal diet, composed almost entirely of aquatic insects, invertebrates and, where available, small fish and fish eggs.

This species’ distinctive traits include frequent dipping, a blinking white eyelid, and vigorous feeding by jumping or diving into turbulent water even at ambient temperatures well below 0°C. To persist in this demanding environment, the American Dipper has a low metabolic rate, extra oxygen-carrying capacity in its blood, and a thick coat of feathers. It aggressively defends both summer territories and winter spaces along streams.

Half a century after Muir’s glowing accounts of the American Dipper in the Sierra Nevada, a number of researchers began to study its life history. Hann (1950) studied nesting behavior on the East River, near Gothic, Gunnison Co., CO. In Missoula Co., MT, Bakus (1959a, b) studied breeding behavior, and population density; Mitchell (1968) studied diet; and Sullivan (1973) studied diet, molt, and adaptations to the aquatic environment. Ealey’s (1977) study on the Sheep River near Calgary, Alberta, reported on ecology and breeding behavior. In a three-year study on Boulder Creek, Boulder Co., CO, Price researched population dynamics (Price 1975, Price and Bock 1983). Working with birds on the Logan River, Cache Co., UT, Fite (1984) analyzed vocal behavior. Additional studies have addressed the species’ physical adaptations (internal and external) to aquatic life (Goodge 1959, 1960; Murrish 1970a, 1970b).

The American Dipper is North America’s only truly aquatic passerine. Most of the information in this account pertains to the subspecies C. m. unicolor, which resides in the United States and Canada (see Systematics: subspecies).